For maintenance of residential indoor air quality, the fresh air flow rates required for the recommended fresh air changes per hour (ACH), based on house size and occupancy level, are prescribed in ASHRAE Standard 62.2, and are given as a theoretical constant rate of fresh air flow replacing outgoing stale air. ACH levels less than the recommendation result in discomfort and building problems, while excessive amounts are uneconomical. Therefore, it is desirable to obtain the prescribed ACH level, and control the fresh air flow rate by means of mechanical ventilation.
Three basic types of fresh air ventilation systems exist: supply-type, consisting of a fresh air intake system only, which tends to pressurize the house, exhaust-type, having only a stale air exhaust system, which tends to depressurize the house, and the balanced-type, having both fresh air intake and stale air exhaust, which tends to maintain a neutral pressure in the house. A balanced type system can also provide the option of employing heat/moisture transfer between the intake and exhaust air streams, by combination with a Heat Recovery Ventilator/Energy Recovery Ventilator (HRV/ERV) or other heat-exchanging device.
The present invention is directed to improvements in whole -house ventilation systems.